1. Field of the Invention
The present invention relates to night vision devices. More particularly, the present invention relates to night vision devices of the type which removably and relatively movably attach to a support structure secured to a face mask or to a helmet, for example, to thereby be supported in front of at least one eye of the user. As thus supported, the night vision device may be used by the wearer of the helmet or face mask to view a night scene while the user's hands remain free. Still more particularly, the present invention relates to such a night vision device having an infrared light which is not visible to the unaided eye. This light may be used, for example, for covert signaling to other personnel who are equipped with night vision viewers. This infrared light may also be used for map reading and for area illumination, for example, without the aid of illumination which is visible to the unaided eye. When the momentary illumination feature of the infrared light is used for a "quick look" illumination of a map or area, for example, the user's safety is improved because the infrared light cannot be forgetfully left on to reveal the user's position to others with night vision devices. The night vision viewer includes a single control switch which controls both the night vision viewer and the infrared light in both its continuous and momentary illumination.
2. Belated Technology
A conventional night vision device is known as the AN/PVS-7B. This night vision device includes a housing with a single objective lens through which low-level light from a night scene is received. The housing of the conventional AN/PVS-7B also included an image intensifier tube which provides a phosphor green light image representative of the low-level light scene viewed through the single objective lens, an image splitter, and a pair of eye pieces in which a user of the device may view the intensified image with each eye.
The conventional AN/PVS-7B also includes a small infrared spot light which is not visible with the unaided eye, and which may be locked on for area illumination, for example, in an area where natural or other low-level lighting is nonexistent or too dim for the night vision device to provide an image. Such an infrared area illumination may be required, for example, in a building basement or in a tunnel where natural light can not reach, and where artificial illumination visible with the unaided eye is not available. This small infrared spot light is also useful for such purposes as map or sign reading in circumstances where visible illumination would be undesirable. Once this infrared spot light is locked on, it stays on until the user purposely turns it off.
However, experience has shown that users of the conventional AN/PVS-7B too often forgetfully leave the infrared spot light on. This spot light is not visible to the unaided eye. But other possibly hostile personnel with night vision devices can seen this spot light for a distance of several kilometers. Thus, the forgetful leaving on of the infrared spot light of the conventional AN/PVS-7B night vision device may reveal the user's existence and location to other personnel within a wide area.
Additionally, experience has also shown that the small infrared spot light can desirably be used for covert signaling purposes to other friendly personnel who are equipped with night vision devices. That is, hostile personnel who are not equipped with night vision devices will not be able to see the covert signaling. Unfortunately, the conventional AN/PVS-7B night vision device uses a control switch configuration for the infrared spot light which requires that the switch knob be pulled axially and then turned to a detent to illuminate and lock on the infrared spot light. Similarly, in order to extinguish the infrared spot light, the switch knob must be rotated out of the detent position, and pushed axially inward.
Consequently, covert signalling with the conventional AN/PVS-7B night vision device is very awkward. Further, because the axial movements of the switch knob require a considerable and deliberately-applied force, the aiming of the night vision device in a particular direction, as well as its position of placement on the user's head may be upset. Moreover, those who attempt covert signaling with the conventional AN/PVS-7B type of night vision device generally find it necessary to stabilize the device with one hand while the other hand is used to manipulate the knob of the control switch. Understandably, this necessity to use both hands for operation of the night vision device in a convert signaling mode undermines the utility of such a head-mounted device. Users of the head-mounted night vision devices most often want to have at least one hand free for other uses while using the night vision device for viewing or signaling.
Moreover, the same deficiency of the conventional AN/PVS-7B type of night vision device becomes apparent when the user wants to take a quick look at a map, street sign, or other such informative material where additional supplemental illumination from the infrared spot light is desired. The conventional control circuitry and switch do not allow the user to illuminate the infrared spot light, and then to quickly extinguish this light as soon as the necessary information has been glimpsed, and before possibly hostile personnel can take aim on the user.
Other conventional night vision devices have employed an infrared spot light controlled by a momentary contact switch. For example, a conventional night vision device has employed a control switch for the night vision device, and a separate push button type of momentary contact switch for operation of the infrared spot light. With this type of conventional night vision device, the housing integrity of the device is more easily compromised by the entry of dirt and water because both the control switch and the push button switch require individual openings in the housing. Further, operation of the device requires the operator to be familiar with the location and operational requirements of both the control switch and the push button switch. Under stressful conditions, the necessity to locate and operate more than one control or switch on a night vision device can be a decided disadvantage.